Living on assumption and promises is more like spending money you haven't received. People can make promises but how sure are you that the promise will be fulfilled.
I agree with your opinion, it is true that we as humans must be able to walk on reality, not on false promises and uncertainty. Hoping for a promise, is indeed very confusing, sometimes the promise is actually fulfilled, but sometimes, the promise lies and is not kept. So all this stuff about promises is very confusing, makes the mind and heart to be confused. But what is certain, we as human beings with common sense, we should be able to choose more, between people who can be trusted and who cannot be trusted. Because if you keep repeating mistakes like you experienced, things like that will cause something negative and disappointing. And don't forget! we ourselves must always keep the promises we have made, so that we can be trusted by others, and are not called people who like to lie.